Dimeric proanthocyanidins from the roots of Ephedra sinica.

Two new dimeric proanthocyanidins, ephedrannin B ( 2) and mahuannin E ( 4), along with two known congeners, ephedrannin A ( 1) and mahuannin D ( 3), were isolated from the roots of Ephedra sinica Stapf. Based on NMR, MS, and CD analysis, the structures of the new compounds were deduced to be 5,7,4'-trihydroxyflavan-[4(alpha)-->8,2(alpha)-->O-->7]-kaempferol ( 2) and 5,7,4'-trihydroxyflavan-[4(beta)-->8,2(beta)-->O-->7]- EPI-afzelechin ( 4). The compounds 1 - 4 were evaluated for cytotoxicity against three tumor cell lines (SGC-7901, HepG2, and HeLa), and 2 was found to be significantly active.